1. Field of the Invention
The present invention relates to a bent wire forming method.
2. Prior Art
Japanese Patent Application Internal Publication No. H11-514493 discloses a conventional example of a method for forming a bent wire that has a bent portion by means of a wire bonding apparatus. In this method, a ball is formed on the tip end of a wire that passes through a capillary and caused to extend from the undersurface of the capillary, and the capillary is lowered so that the ball is bonded to an electrode pad. Then, the capillary is moved along a curved path, thus forming a bent wire shape. Further, the capillary is raised from a wire cutting position, and a bent wire is finally formed by cutting the wire by means of an electronic flame jet or by using a mechanical means such as a knife.
Generally in a wire bonding apparatus, a back tension is applied to the wire that passes through the capillary so that a constant tension is applied to the wire. In addition, a wire clamper is installed above the capillary in order to hold the wire.
In the above-described prior art, the wire is cut after the bent wire shape has been formed by moving the capillary. As a result, it has several problems. When the bent wire shape is formed by the moving capillary, it is necessary to pay out the wire from the capillary; accordingly, the wire clamper is in an open state. As a result, the bent wire shape that exists prior to cutting is pulled upward and deformed by the back tension that is applied to the wire. Thus, a stable shape cannot be obtained. Furthermore, a bent wire shape is formed simply by moving the capillary along the bent wire shape that is to be formed. Accordingly, the shapes of the bent portion and inclined portion of the bent wire are deformed by the elastic force of the wire. This also makes it impossible to obtain a stable shape.
Accordingly, the first object of the present invention is to provide a bent wire forming method which produces a wire with a stable high-quality shape without this shape being affected by the back tension that is applied to the wire.
The second object of the present invention is to provide a bent wire forming method in which the excess elastic force of the wire is absorbed so that a constant amount of elastic force is obtained, thus forming an even more stable high-quality shape.
The third object of the present invention is to provide a method for forming a bent wire with a stable, constant length, in which the wire length above the ball that is bonded to an electronic circuit element, etc. can be set as desired, so that the method involves no increase in cost, and the length of the pin-form wire can be consistent.
The above-described first object is further accomplished by unique steps of the present invention for a bent wire forming method, and the unique steps of the present invention comprises: forming a pin-form wire by means of a wire bonding apparatus; moving a capillary of the wire bonding apparatus along a curved path with the pin-form wire inserted in the capillary and with a wire separated from the pin-form wire inside the capillary.
The above-described first object is accomplished by unique steps of the present invention for a bent wire forming method, and the unique steps comprises: forming a pin-form wire by means of a wire bonding apparatus; and moving a capillary of the wire bonding apparatus along a curved path with the pin-form wire inside the capillary.
The above-described first object is still further accomplished by unique steps of the present invention for a bent wire forming method, and the unique steps of the present invention comprises: forming a pin-form wire by means of a wire bonding apparatus; allowing the pin-form wire to be entered into an empty capillary and moving the capillary along a curved path.
Furthermore, the above-described pin-form wire is formed by the steps of: forming a ball on a tip end of a wire that passes through the capillary; allowing the wire to extend from a lower end of the capillary; forming a notch in a portion of the wire located between the ball and the capillary using a notching means that is installed in the wire bonding apparatus; bonding the ball to an electrode pad of an electronic circuit element by the capillary; raising the capillary; and pulling the wire upward to cut the wire at the notch.
In addition, in the present invention, the pin-form wire can be formed by a wire bonding apparatus that includes a first wire clamper that is movable in a vertical direction along with the capillary and a second wire clamper that is immovable in a vertical direction; and with this boding apparatus, the pin-form wire is formed by the steps of:
forming a ball on a tip end of a wire passing through the second wire clamper, first wire clamper and capillary, the second wire clamper being opened and the first wire clamper being closed;
opening the first wire clamper so as to render the ball to contact a lower end of the capillary as a result of an action of a back tension applied to the wire;
lowering the capillary and first wire clamper;
raising the capillary and first wire clamper after closing the second wire clamper so as to cause the wire to extend from the lower end of the capillary;
closing the first wire clamper and opening the second wire clamper, then forming a notch in a portion of the wire located between the ball and the capillary using a notching means of the wire bonding apparatus;
opening the first wire clamper and lowering the capillary and first wire clamper so as to bond the ball to an electrode pad of an electronic circuit element by the capillary; and
raising the capillary and first wire clamper and closing the first wire clamper at an intermediate point during the raising movement of the capillary and first wire clamper, thus pulling the wire upward and cutting the wire at the notch.